In general, the amount of use of water increase as society develops, and every country has an interest in improving the efficiency of removal of nitrogen and phosphorous in treating of various waste waters including urban sewage. This is because nutritive salts accelerate eutrophication and thus lower usefulness of valuable water resources and damage the ecosystem. It is a real circumstance that the problem of eutrophication spreads to almost all natural water systems and frequently occurs everywhere. In a trend that management of water quality is recently tightened, it is of course that allowed emission concentration for contaminants of emission source has to meet allowed emission criteria or criteria for the quality of discharged water, and total emission of contaminants for each water system is managed according to regulation of total emission and thus allowed concentration for contaminants of emitted water is forecasted to be further tightened for water system with a high contamination load.
An active sludge process widely used as method of secondarily treating the sewage is effective in removing of organic matter and floating matter. However, in a case where it is necessary to remove the nutritive salts, the efficiency of removal of the nitrogen and phosphorous is not particularly high, and therefore an improvement is needed. Biological advanced wastewater treatment for removing the nutritive salts such as the nitrogen and phosphorous etc. basically consists of oxygen-free step, anaerobic step, aerobic step and precipitation step, and treatment process is determined by properly combining these steps depending on the contamination load or the characteristic of contamination source. The advanced wastewater treatment method is practically used as various methods such as SBR, A2/O, MLE etc. depending on modes of installing and running of treatment facilities.
In recent, KSMBR (Kwater Kms Ssangyong Membrane Bio Reactor) is provided for treating the sewage. As illustrated in FIG. 1, this sewage treatment method is a process in which the sewage generated at home etc. is introduced into a flow rate adjustment tank and then into an anaerobic tank, in which the phosphorous is emitted by using the organic matter, and thereafter, the sewage is fed into alternate reaction tanks which are arranged in parallel and run in the modes of nonaeration-aeration-nonaeration and nonaeration, in which the nitrogen is treated, and then is fed into a membrane separation aerobic tank, in which the contaminants are separated into solid and liquid by separation membranes and thus the floating matter and colonbacillus are removed, and then the sewage is introduced into a dissolved oxygen-decreasing tank, in which the nitrogen (N) and phosphorous (P) are removed, and then is fed back to the anaerobic tank to be treated, and generated sludge is fed to a sludge storage tank and separately treated. Such a process is advanced sewage treatment technique which treats the organic matter, nitrogen and phosphorous and performs solid-liquid separation by means of a filtering membrane.
However, in the sewage treatment process of such a method, in order to remove the contaminants adhering to hollow fiber membranes of separation membrane cartridges installed in the membrane separation aerobic tank for solid-liquid separating of the contaminants, the separation membrane cartridges are removed and then are cleaned one by one directly by a worker at workplace using a fire-extinguishing hose, to thereby remove the contaminants, which is inconvenient.